Recently, with regard to processing of a silver halide photographic light sensitive material (hereinafter, simply referred to as photographic material), shortening of processing time and curtailment of processing effluent have been demanded. In the field of medical use, the amount of X-ray photographing time is rapidly increasing due to increased use of X-rays for diagnosis and inspection in general medical examinations, as well as spread of periodical medical check-ups and clinical surveys. As a result, desire for still faster processing and reduction of processing effluent is raised.
Shortening of processing time including developing, fixing, washing, drying, etc. is the key for faster processing of photographic materials. Shortening of the developing time alone, however, leads to a marked decrease of image density and sensitivity and deterioration of contrast. Shortening of the fixing time alone leads to insufficient fixing, causing deterioration of image quality. Accordingly, it is basically required to enhance developability, fixability and dryability of a photographic material in concert.
It is conventionally believed that lowering the content of silver iodide with low solubility, the use of a silver chlorobromide or silver chloride emulsion with high solubility, the decrease of the silver halide grain size and the use of tabular-formed grains are advantageous for enhancement of developability and fixability. However, it is also known that lowering the silver iodide content and the use of a silver chlorobromide or silver chloride emulsion cause a decrease in sensitivity.
Techniques which incorporate silver halide solvents (thiocyanates) in a silver halide emulsion or a photographic material for the purpose of enhancement of sensitivity and developability are described in U.S. Pat. Nos. 2,222,264 and 3,320,069, and JP-A 62-18538 (the expression, "JP-A" means unexamined, published Japanese Patent Application). However, enhancement of the sensitivity by the use of the silver halide solvent leads to deterioration of storage stability, causing practical problems in use of the solvent.
It is known in the field of photographic printing papers that, as a method for sensitizing silver chloride grains, high sensitivity can be achieved by incorporating a compound of group VIII metal of the periodic table, within the grains. This effect concerns only cubic or octahedral grains, and effects concerning tabular grains are not known at this time.
For enhancement of developability to reduce processing effluent, it is desirable to use silver halide grains with high covering power whereby a high density can be obtained with a low silver coverage. The tabular grains are suitable therefore in terms of sensitivity, graininess, sharpness and spectral sensitization efficiency. On the other hand, as the size or thickness of silver halide grains decreases, scattering of blue light due to developed silver increases, resulting in strongly yellowish light to form an yellowish silver image.
With regard to techniques for modifying silver image tone, there have been reported a number of studies of photographic materials and processing. For example, specific mercapto compounds are well-known as a representative image toner. Recently, there has been proposed a technique in which a specific dye is dissolved in a water insoluble high boiling solvent, dispersed in water and incorporated in a photographic material, as described in JP-A 5-165147. However, it resulted in fluctuation in sensitivity, depending on the aging condition thereof before exposure. In X-ray photographic materials for medical use, there have been problems such as dirt adhering to the intensifying screen which is brought into contact with a photographic material at the time of exposure. Furthermore, in the above technique, since the same amount of dye as that of an exposed portion is contained in a non-exposed portion, there is the defect of increased fog density.
To overcome this defect, JP-A discloses a technique in which with forming a silver image, a dye image is formed, in response to the silver image, from a diffusion-proof compound capable of releasing a diffusible dye upon reaction with a silver ion, but the decreased effects of improving blackness of the silver image and lowering of the fog density were insufficient.
JP-A 3-153234 discloses a technique of using a leuco dye capable of forming a blue dye image in response to a silver image. Thereby, contamination of a developer and occurrence of stains can be minimized but since color tone of the blue dye formed from the leuco dye is in a longer wavelength region and has a greenish tint, the improvement in blackness of the silver image was insufficient. In addition, there was a defect such that leuco dye residue in a non-exposed portion of a processed photographic material is liable to color-form with aging, causing an increase of fog density.